Traditional spark plug construction includes a generally cylindrical shell body having a pair of ends, one of which is threaded. A co-axial ceramic insulator extends along the central axis of the cylindrical shell body from the threaded end through the shell body and beyond the opposite end. A co-axial center electrode extends along the central axis of the cylindrical shell body. The co-axial center electrode is exposed near the threaded end of the cylindrical shell body and is electrically connected through the insulator to a terminal. The terminal is connected to a spark plug wire which is used to provide a voltage signal to the center electrode. An "L" shaped ground electrode typically extends from the threaded end of the shell body forming a spark gap between the ground electrode and the center electrode. The spark gap is set to a pre-selected distance based on the internal combustion engine, i.e. the typical air-fuel mixture in the combustion chamber and the amount of energy that is required to combust the typical air-fuel mixture.
Several problems, such as carbonization, erosion, and pitting of spark plug components, typically center and ground electrodes that substantially reduce the life of the spark plug thereby requiring frequent replacement under normal operation of the internal combustion engine. Engines that require a lean air-fuel mixture run into a problem of maintaining complete combustion. Typically, spark plugs are designed based on air-fuel mixtures that will ignite over a broad range of applications. Having spark plug designs that are capable of operating with complete combustion for lean air-fuel mixtures requires a substantial energy level. In comparison, spark plugs designed using the substantial energy level for non lean air-fuel mixtures may have high current discharge and cause premature wear of the center and ground electrodes of the spark plug.
One of these problems involves carbonization and the depositing of lead, lead oxides, and other contaminants in and around the center and ground electrodes during the course of repeated electrical discharges. The contaminants that are deposited on the electrodes alter the impedance between the center and ground electrodes. The alteration of the impedance may cause the spark plug to have a weak spark or not to spark. The weak spark is due to the contaminants filling the gap between the center and ground electrodes allowing leakage of electrical energy between the center electrode and the ground electrode. Spark plugs that do not spark are when too much electrical energy is flowing from the center electrode to the ground electrode. To ensure proper operation, the engine spark plugs often need to have the electrodes cleaned of any contaminants or the spark plug is often replaced. The weak spark causes incomplete combustion of the air-fuel mixture in the combustion chamber which increases pollutants that are emitted from the engine and decreases the efficiency of the engine. Spark plugs that do not spark expel the air-fuel mixture from the combustion chamber and into the exhaust which increases pollutants that are emitted from the engine and decreases the efficiency of the engine.
Another problem occurring with conventional spark plug design is pitting and general physical deterioration of the center and ground electrodes after a certain period of operation. Pitting of the spark plug electrodes may increase the effective spark gap, thereby increasing the electrical potential needed for discharge. Pitting results in weak sparks and could ultimately lead to failure of the spark plug to spark.
Another problem that typically occurs with conventional spark plug design is maintaining complete combustion when a lean air-fuel mixture is desired for combustion. The lean air-fuel mixture requires a substantial level of energy and breakdown voltage from the ignition source (e.g. spark plug) to ignite the lean air-fuel mixture within the combustion chamber for complete combustion. The substantial level of energy in a spark ignited engine can lead to increase pitting and carbonization of the electrodes which requires replacement of the spark plug. Engines with lean air-fuel mixtures that operate using a lower level of energy in an attempt to minimize deterioration of the center and ground electrodes typically have incomplete combustion which increases the pollutants that are emitted from the engine. Incomplete combustion has undesirable exhaust byproducts, such as particulate matter. Regulation of exhaust byproducts are causing engines to be designed with ignition systems that maintains a more complete combustion thereby increasing the level of energy which may cause high current discharge, carbonization, and/or pitting of spark plug electrodes.
The present invention is directed to overcoming one or more of the problems as set forth above.